1. Field of the Invention
The present invention is directed to a shockwave source for extracorporeal treatment of a calculus disposed in the body of a patient by disintegrating the calculus with shockwaves, and in particular to such a shockwave source operating on the principle of a rapid electromagnetic repulsion of a membrane to generate the shockwaves.
2. Description of the Related Art
Shockwave generators are generally known in the art of the type having a coil mounted within a coil carrier and an electrically conductive membrane spaced from and insulated from the coil. Generally a sack filled with a fluid coupling agent is provided at a side of the shockwave source intended to be applied to a patient, with shockwaves generated by the membrane traveling through the coupling agent to the patient upon rapid energization of the coil, and the subsequent rapid repulsion of the membrane therefrom.
It is also generally known to make use of an ultrasound transmission and reception system combined with the shockwave generator to transmit an acoustic signal to the patient, and to receive echo signals from the patient, for locating and observing the calculus.
German OS 33 28 051 and corresponding to U.S. Pat. No. 4,674,505, discloses a shockwave generator having a shockwave tube in the form of a jacket, and a shockwave source of the type described above having a flat coil and a copper membrane separated therefrom by an insulating foil. An acoustic converging lens is disposed in the shockwave tube, and it focuses the planar shockwaves generated by the membrane to a focal point, and also forms the exit of the shockwave tube for the shockwaves. For applying the shockwave tube to the patient, the open portion of the tube lying opposite the membrane is closed with a sack which is filled with a coupling agent, as is the entire shockwave tube. The shockwave generator consisting of the shockwave tube and the shockwave source is moved toward a patient until the calculus to be disintegrated is situated in the focal point of the accoustic lens. The sack filled with coupling fluid is applied against the surface of the patient, so it is insured that the shockwaves always proceed within the fluid.
Published European application No. 0,081,639, corresponding to U.S. Pat. No. 4,539,989, discloses a locating device for a shockwave generator having two x-ray tubes with associated image intensifiers, or two ultrasound transducers, which are laterally attached to the shockwave generator. Using either the x-ray tubes or the ultrasound transducers, it is possible to observe the disintegration of the calculus during treatment. Locating of the calculus and adjustment of the shockwave generator relative thereto, however, are rendered more difficult due to the different irradiation directions of the shockwave generator and of the locating system. Moreover, because the locating system is laterally attached to the shockwave generator, the overall system is larger, so that manipulation thereof is more difficult.
Another shockwave generator is described in German OS No. 33 28 039, particularly in FIGS. 1 and 3 thereof. An ultrasound head of an ultrasound transmission and reception system for locating and observing the calculus is disposed next to or between a plurality of shockwave sources. This arrangement has the same disadvantages as the aforementioned arrangement in that the lateral placement of the ultrasound head requires additional structural volume, and under certain conditions this arrangement makes locating and observing the calculus more difficult.
Published European application 0 148 653, corresponding to U.S. Pat. No. 4,617,931, also discloses a shockwave source using an ultrasound locating system. In this structure, however, the shockwave source does not operate according to the electromagnetic repulsion principle. This shockwave source consists of a plurality, for example 300 or 400, of piezoelectric elements. Because each piezo-electric element can generate an acoustic pulse independently of the others, the omission of one or more of those elements does not significantly influence the operation of the shockwave source. For the purpose of ultrasound locating, it is therefore easily possible to replace one or more of the piezo-electric elements by the ultrasound probe or head of an ultrasound locating system.
A copending application relating in subject matter to the present application is U.S. Ser. No. 105,004, filed Oct. 6, 1987 (Reichenberger and Schittenhelm). This application is assigned to the same assignee as the present application. As shown in FIG. 3 of this related application, a shockwave generator is provided with a central opening in certain components of the shockwave source, with the transmission and reception head of an ultrasound locating device being received in the opening. In this structure, however, the ultrasound head does not project through the membrane, and the membrane remains at all times disposed between the ultrasound head and the patient. The ultrasound signals, both upon transmission and reception, must therefore pass through the membrane, and are attenuated thereby.